静态代码块 非静态代码块和构造函数执行顺序

class B
{
static int a = 0;
{
  System.out.println("B.scope is running");
  a = 10 ;
}
static
{
  System.out.println("B.static  scope is running");
  a = 20;
}
public B()
{
  a = 30;
  System.out.println("B.Constructor  is running");
}

public static void main(String arg[])
{
  System.out.println(B.a);
  System.out.println(B.a);
     B b1 = new B();
  B b2 = new B();
  System.out.println(b1.a);
  System.out.println(b2.a);
  System.out.println(B.a);

}

}

运行结果为：

B.static  scope is running
20
20
B.scope is running
B.Constructor  is running
B.scope is running
B.Constructor  is running
30
30
30

当我们在使用B类时，JVM将B的定义装载，这时它调用了B的静态定义初始化和静态代码块 由于是静态的，尽管我们打印了两次，静态定义初始化和静态代码块都只执行了一次。构造函数是后于非静态代码块执行的.
在屏蔽了Class B中的main方法后,我们再写一个C类继承B类,如下:
class C extends B
{
static int c = 0;
static
{
  c = 10;
  System.out.println("C.static code is runnning and now c is " + c);
 
}
{
  c = 20;
  System.out.println("C.non-static code is runnning and now c is " + c);
 
}

public C()
{
  c = 30;
  System.out.println("C.constructor is running and now c is " + c);
}
public static void main(String args[])
{
  System.out.println(C.c);
  System.out.println(C.c);
  C c1 = new C();
  C c2 = new C();
  System.out.println(c1.c);
  System.out.println(c2.c);
  System.out.println(C.c);
 
}
}

B.static  scope is running
C.static code is runnning and now c is 10
10
10
B.scope is running
B.Constructor  is running
C.non-static code is runnning and now c is 20
C.constructor is running and now c is 30
B.scope is running
B.Constructor  is running
C.non-static code is runnning and now c is 20
C.constructor is running and now c is 30
30
30
30

在此描述一下c变化过程，虽然定义了两个对象c1,c2但其实只有一份共有的c,c被装载时先被初始化为0,后来执行静态代码块时被初始化为10，接着执行c1的非静态代码快时被初始化为20，然后是c1的构造函数被出化为30，然后轮到c2的非静态代码块，这是又重新被初始化回20，然后c2的构造函数，变为30.